Auxiliary Coil Excitation (PMG-I)

Roger Rosborough
Market Development Consultant 
Caterpillar (NI) Limited
Electric Power Product Group
April  2015

ABSTRACT

Cat® generator sets assembled at the Caterpillar facility in Piracicaba, Brazil, known as Power Systems Brazil (PSB), use alternators that feature an auxiliary coil (or auxiliary winding) and permanent magnets in the exciter stator. This provides the benefits of an alternator fitted with a Permanent Magnet Generator (PMG), within the same physical envelope of a self-excited alternator. This includes the capability of sustaining a 300 percent, short-circuit current and not needing to flash the alternator following extended periods of inactivity.